For exact camera positioning for close-up, macrophotography and copying. Two positioning scales are perpendicular to one another. Setting range each 95 mm (3.7 in.). Prismatic precision guideways with micro adjustment across helical gear rack-and-pinion assemblies complete with lock screws and dials calibrated in millimeters. (Kaiser)
However your version has mounted in addition:
-) a rectangular gusset with 1/4" screw at base mount
-) a rectangular gusset fitting both racks
yielding a further 90° off-set in both cases.